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Overview

GeocodingService is a Swift actor that provides geocoding functionality for city name searches. It uses the Open-Meteo Geocoding API to find cities by name and return their geographic coordinates and metadata. 
actor GeocodingService
Source: BreezeApp/Services/GeocodingService.swift:4

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Actor Isolation

This service is implemented as an actor to ensure thread-safe access to its methods and properties. All async methods are actor-isolated and can be safely called from any context.

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Shared Instance

static let shared = GeocodingService()
A singleton instance of the service that can be accessed throughout the application.

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Methods

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searchCities

Search for cities by name and return matching results with geographic coordinates. 
func searchCities(
    query: String
) async throws -> [City]
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query
String
required
The city name or partial name to search for. Must be at least 2 characters long.
Returns: [City] - An array of City objects containing:
  • City name
  • Country information
  • Latitude and longitude coordinates
  • Additional metadata (population, timezone, etc.)
Returns an empty array if the query is less than 2 characters. Throws:
  • URLError.badURL - If the URL cannot be constructed
  • URLError.badServerResponse - If the server returns a non-200 status code
  • DecodingError - If the response cannot be decoded
Implementation Details: The method constructs a URL with the following query parameters:
  • name: The search query string
  • count: Maximum number of results (set to 5)
  • language: Language for results (set to “en” for English)
  • format: Response format (set to “json”)
The minimum query length of 2 characters helps prevent unnecessary API calls for single-character searches. 
// Early return for short queries
guard query.count >= 2 else { return [] }

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Usage Example

import SwiftUI

struct CitySearchView: View {
    @State private var searchText = ""
    @State private var cities: [City] = []
    @State private var isLoading = false
    @State private var errorMessage: String?
    
    var body: some View {
        VStack {
            TextField("Search cities", text: $searchText)
                .textFieldStyle(.roundedBorder)
                .padding()
                .onChange(of: searchText) { newValue in
                    Task {
                        await searchCities(query: newValue)
                    }
                }
            
            if isLoading {
                ProgressView("Searching...")
            } else if let error = errorMessage {
                Text("Error: \(error)")
                    .foregroundColor(.red)
            } else {
                List(cities) { city in
                    VStack(alignment: .leading) {
                        Text(city.name)
                            .font(.headline)
                        Text("\(city.country) - Lat: \(city.latitude), Lon: \(city.longitude)")
                            .font(.caption)
                            .foregroundColor(.secondary)
                    }
                }
            }
        }
    }
    
    func searchCities(query: String) async {
        guard query.count >= 2 else {
            cities = []
            return
        }
        
        isLoading = true
        errorMessage = nil
        
        do {
            let service = GeocodingService.shared
            cities = try await service.searchCities(query: query)
        } catch {
            errorMessage = error.localizedDescription
            cities = []
        }
        
        isLoading = false
    }
}

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Simple Usage

// Basic search
let service = GeocodingService.shared

do {
    let cities = try await service.searchCities(query: "San Francisco")
    
    for city in cities {
        print("\(city.name), \(city.country)")
        print("Coordinates: \(city.latitude), \(city.longitude)")
    }
} catch {
    print("Search failed: \(error)")
}

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API Endpoint

The service uses the Open-Meteo Geocoding API: 
https://geocoding-api.open-meteo.com/v1/search

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Source Code

import Foundation

/// Service for geocoding city searches using Open-Meteo API
actor GeocodingService {
    static let shared = GeocodingService()
    
    private let baseURL = "https://geocoding-api.open-meteo.com/v1/search"
    
    /// Search for cities by name
    func searchCities(query: String) async throws -> [City] {
        guard query.count >= 2 else { return [] }
        
        var components = URLComponents(string: baseURL)!
        components.queryItems = [
            URLQueryItem(name: "name", value: query),
            URLQueryItem(name: "count", value: "5"),
            URLQueryItem(name: "language", value: "en"),
            URLQueryItem(name: "format", value: "json")
        ]
        
        guard let url = components.url else {
            throw URLError(.badURL)
        }
        
        let (data, response) = try await URLSession.shared.data(from: url)
        
        guard let httpResponse = response as? HTTPURLResponse,
              httpResponse.statusCode == 200 else {
            throw URLError(.badServerResponse)
        }
        
        let decoder = JSONDecoder()
        let result = try decoder.decode(GeocodingResponse.self, from: data)
        
        return result.results ?? []
    }
}

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Performance Considerations

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Query Debouncing

When implementing search-as-you-type functionality, consider debouncing the search to avoid making excessive API calls: 
import Combine

class CitySearchViewModel: ObservableObject {
    @Published var searchText = ""
    @Published var cities: [City] = []
    
    private var cancellables = Set<AnyCancellable>()
    private let service = GeocodingService.shared
    
    init() {
        $searchText
            .debounce(for: .milliseconds(300), scheduler: DispatchQueue.main)
            .removeDuplicates()
            .sink { [weak self] query in
                Task {
                    await self?.search(query: query)
                }
            }
            .store(in: &cancellables)
    }
    
    func search(query: String) async {
        do {
            cities = try await service.searchCities(query: query)
        } catch {
            print("Search error: \(error)")
            cities = []
        }
    }
}

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Error Handling Best Practices

enum GeocodingError: LocalizedError {
    case queryTooShort
    case networkError(Error)
    case noResults
    
    var errorDescription: String? {
        switch self {
        case .queryTooShort:
            return "Please enter at least 2 characters to search"
        case .networkError(let error):
            return "Network error: \(error.localizedDescription)"
        case .noResults:
            return "No cities found matching your search"
        }
    }
}

func searchCitiesWithCustomError(query: String) async throws -> [City] {
    guard query.count >= 2 else {
        throw GeocodingError.queryTooShort
    }
    
    let service = GeocodingService.shared
    
    do {
        let cities = try await service.searchCities(query: query)
        
        guard !cities.isEmpty else {
            throw GeocodingError.noResults
        }
        
        return cities
    } catch {
        throw GeocodingError.networkError(error)
    }
}

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See Also

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